(1) Field of the Invention
This invention relates to the filtration of lake or pond water flowed at great rates to condensors of industrial plants.
(2) Description of the Prior Art
Certain large industrial processes, such as steam-operated electrical generating power plants, use great quantities of circulating water on a continuous basis. The circulating water is usually flowed through tubes of a condensor or heat exchanger to absorb heat from another fluid, such as steam. For example, a medium-sized power plant might require 250,000 gallons per minute of the circulating water (gpm) flowing through a ten foot diameter tunnel from a lake to the plant. Of course, for larger power plants, more circulating water is required.
Lakes or ponds used as sources of circulating water often contain fish, clams, and other water life. In certain areas, especially during warm, temperate periods, clams flourish and multiply in the lakes or ponds. Before my invention, small clams, and other particles were drawn into the power plant with the circulating water. Any clams or other particles larger than a maximum allowable particle size clog the condensor tubes used in the plant. Unclogging the tubes often requires shutting down the plant, at great expense.
Before my invention, it was commercial practice to use a traveling screen in the lake at the pump input. However, this solution to the clam clogging problem has been ineffective.
Before this application was filed, a search was made in the U.S. Patent and Trademark Office. That search developed the following U.S. patents:
______________________________________ PETERSON 211,640 RONNINGEN ET AL 2,828,017 LIDDELL 2,954,872 LIDDELL 3,056,499 OBIDNIAK 3,675,775 KAISER 3,976,577 SCHAEFFER 3,994,810 ______________________________________
PETERSON shows that over 100 years ago, it was known to filter large volumes of water by using parallel filters. He also provided structure that could isolate each of the filters so one filter could be taken out of service at a time for cleaning or repair while the remaining filters were still operating.
LIDDELL U.S. Pat. Nos. 2,954,872 and 3,056,499 shows a series of three filters where any one of the three filters can be taken out of service and backwashed. LIDDELL apparently used full flow backwash by reversing the main flow through the filter and backwashing the filter with filtered water.
The other patents are considered pertinent because the applicant believes the Examiner would consider anything revealed by the search to be relevant and pertinent to the examination of this application.